FIG. 4.

Mamu-B*17-positive animals recognize common escape variants of Mamu-B*17-restricted epitopes. IFN-γ ELISPOT responses to titrated peptides representing wild-type and common escape variants of the four primary Mamu-B*17-restricted epitopes, Vif HW8 (left panels), Nef MW9 (second from left), Nef IW9 (second from right), and Env FW9 (far-right panels). The autologous (aut) viral sequences (the epitope sequences at the time of ELISPOT testing) are in insets in each panel, aligned to wild-type (wt) SIVmac239. Five chronically infected animals were tested: progressors r02039 (a) and r90092 (b), former EC r96112 (c), and ECs r95071 (d) and r98016 (e). (f) Animal r95071 harbored SIV with an M-to-I variant of the MW9 epitope at position 1 after experimental in vivo CD8 cell depletion (experiment done in reference 19), but currently harbors an M-to-T variant. The M1I-specific response greatly expanded upon return of CD8⁺ cells, while wild-type-specific cells did not (g). All ELISPOTS (in panels a to e and g) were performed in duplicate. Responses were measured as spot-forming cells (SFC) per million PBMCs. The mean number of spots in unstimulated (no peptide) wells was subtracted from each well. ELISPOT responses were considered positive if the number of spots (per million PBMCs) in replicate wells exceeded the background plus two times the standard deviation and was >50. Error bars represent the mean ± standard error for each measurement. The horizontal line in panels a thru e is the cutoff for what is considered positive.